Yeah, live load makes a big difference.  Lots of live load in a small box, the 
color of the box does not matter much.
Little live load in a large box, color makes all the difference.  

From: castarritt . 
Sent: Friday, August 16, 2019 8:16 AM
To: AnimalFarm Microwave Users Group 
Subject: Re: [AFMUG] Solar load

All of our DDB boxes have the brushed metal finish.  I painted one of them with 
some white elastomeric roof coating stuff from Lowes that is meant to reflect 
solar energy, and the peak internal temp only went down ~5°F.  We have a lot of 
gear in that box, so I think an application with a larger ratio of solar gain 
to internal heat generation would benefit more.  After the paint failed to 
solve the problem, I replaced the 110cfm fans with a pair of 48vdc 250+cfm 
fans, and the temp went down 20°F; it does make a lot more noise though.

On Thu, Aug 15, 2019 at 6:31 PM Ken Hohhof <> wrote:

  The difference between standard machine grey and just bright white spray 
paint from the hardware store is dramatic.  I suspect everything beyond that is 

  Also back around 2005 when I ordered my first outdoor cabinet from DDB, I 
thought I wanted unpainted metal aluminum since all the traffic control boxes I 
see are plain metal or stainless steel.  The salesperson said I absolutely 
didn’t want plain metal because it would get hot in the sun and what I wanted 
was the cream color.

  From: AF <> On Behalf Of Bill Prince
  Sent: Thursday, August 15, 2019 6:19 PM
  Subject: Re: [AFMUG] Solar load

  If you look up insulating paint on Wikipedia, the entry there says all 
ceramic heat-reflective coatings are snake oil.

  I did find a good discussion on Scientific American 
They don't exactly describe it as snake oil, but they also suggest that you not 
get your hopes up.

  I suspect you can get your best results with a coat of reflective white 
paint, and try to keep it clean.

bp<part15sbs{at}gmail{dot}com> On 8/15/2019 1:12 PM, wrote:

    Be interesting to do a bake off between this and the plain “satellite 
white” I use.  

    I have always found it interesting that highly reflective things like 
polished aluminum, chrome and silver paint seem to be really bad at reflecting 
heat/sun.  But we have all grabbed a chrome wrench that has been left in the 
hot summer sun and realized hot much it absorbs.  I am guessing what we see as 
reflective, Infra Red sees as flat black.  

    From: Bill Prince 

    Sent: Thursday, August 15, 2019 1:46 PM


    Subject: Re: [AFMUG] Solar load

    Which reminds me of this material that a friend clued me in on. 

    You can get this at Home Depot (for example). It is pricey; around $250 per 
5 gallon bucket, AND it needs a top coat of another material at near the same 
price. However, for an advertised reduction in temperature of over 60 degrees 
F, it may be worth a look.

bp<part15sbs{at}gmail{dot}com> On 8/15/2019 12:35 PM, Lewis Bergman wrote:

      I remember Chuck doing a study on this same subject so I thought there 
might be some interest.

      Cabinet heat load


      Lewis Bergman 

      325-439-0533 Cell


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